The impact of two nonionic surfactants, namely Span 20 and Span 85, on the electrorheological response and colloidal stability of urea-coated barium titanyl oxalate (BTRU)/silicone oil suspensions is investigated. We quantitatively analyze the surfactant effect on modified ER performance through the measurements of yield stress and current density, as well as the tuned suspension stability through calculation of the Turbiscan stability index (TSI) and naked-eye observations of sedimentation phenomena. The surfactant effect on particle–oil interactions and agglomeration effects is examined by measuring the permeability of silicone oil when mixed with the Span surfactant and the cluster size of particles in dispersing medium, respectively. Our results indicate that with the presence of a Span surfactant, the yield stress of the suspension exhibits a local maximum at certain Span concentrations. We hypothesize that below the optimal Span concentration, the ER properties are enhanced by the increase of the electrostatic interaction between particles. Above the limiting concentration, the ER activity is weakened by the formation of a double-layer surfactant structure that generates a steric hindrance effect. We discover that the addition of the Span surfactant favors the improvement of the particle agglomeration phenomenon, thereby promoting colloidal stability of the suspension. Consequently, in the consideration of both ER properties and suspension stability, an optimal ER fluid with the addition of 0.4 wt% Span 85 is acquired with remarkable integrated ER properties.
Solid dispersions (SDs) possess the potential to enhance the bioavailability of insoluble active pharmaceutical ingredients (APIs) by effectively converting them into amorphous state. However, SDs have a tendency to recrystallize unless appropriate excipients are employed. The objective of this study was to evaluate the ability of hypromellose acetate succinate HF (HPMCAS-HF) and Soluplus® to inhibit the recrystallization of β-carotene and improve its in vivo bioavailability through the fabrication of ternary β-carotene solid dispersions (SDs) with the aid of specific surfactant. Due to rapid micellization , the dissolution profiles of β-carotene SDs based on HPMCAS-HF/Span 20 (5:5, w/w) or Soluplus®/Span 20 (6:4, w/w) combinations exhibited significant improvement, which were almost 7–10 times higher than β-carotene bulk powder. DSC and PXRD analysis indicated a notable reduction in the crystallinity degree of β-carotene within the SDs. The stability study demonstrated a half-life of β-carotene in the SDs exceeding 30 days. Additionally, the in vivo pharmacokinetics analysis confirmed that the cellulose derivatives/surfactant combinations significantly enhanced the bioavailability of β-carotene by 1.37-fold and 2.3-fold, respectively. Notably, the HPMCAS-HF/Span 20 combination exhibited superior performance. Consequently, the HPMCAS-HF/Span 20 combination held potential for the advancement of an effective drug delivery system for β-carotene.
Psoriasis is a severe disfiguring skin disease affecting approximately 3% of people worldwide and negatively affecting their daily lives. The pathogenesis of psoriasis is complicated, and typical therapeutic strategies for psoriasis mainly focus on anti-inflammation. Considering the side effects, withdrawal rebound, high cost, and many other disadvantages of existing treatments, we developed a new topical therapeutic formulation consisting of niosomes loaded with celastrol, a triterpenoid extracted from Tripterygium . Celastrol niosomes were prepared by the thin film hydration method and probe sonication. The niosomes were composed of Span 20, Span 60, and cholesterol at a weight ratio of 3:1:1. The particle size of the niosomes was approximately 147 nm, with yield of up to 90%. Celastrol niosomes showed improved in vitro permeation ability compared to the raw drug. In our in vivo study, celastrol niosomes effectively alleviated erythema and scaling on the dorsal skin of psoriasis mouse models. Spleen weight and the levels of cytokines, including IL-22, IL-23, and IL-17, decreased after the treatment, indicating the high therapeutic potential of this formulation for psoriasis. In conclusion, encapsulation of celastrol by niosomes increased the water-solubility and permeation of celastrol into the skin, significantly improving its anti-psoriasis activity in mice.
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